1. FIELD
Polymers having electrostatic dissipative properties.
2. PRIOR ART
This invention is an improvement on the inventions described and claimed in U.S. Pat. Nos. 4,588,773 (Federl et al I) and 4,775,716 (Federl et al II) and U.S. Pat. application Ser. No. 59,178, filed Jun. 8, 1987, now U.S. Pat. No. 4,857,590 (Gagger et al), all of which are assigned to the predecessor of the present application's assignee.
Federl et al I relates to the use of an ABS graft copolymer containing a copolymer of epichlorohydrin and an oxirane composition, ethylene oxide. Federl et al II, a continuation-in-part of Federl et al I, also concerns an antistatic graft ABS, but contains smaller amounts of an epichlorophyorin/oxirane copolymer having a somewhat higher ratio of ethylene,. oxide to epichlorohydrin in said copolymer. U.S. Pat. No. 4,857,590 (Gaggar et al) is directed to the use of an alkyl methacrylate polymer to compatibilize the antistatic composition with the ABS polymer.
Barnhouse et al, U.S. Pat. No.4,719,263, discloses that the antistatic properties of various polymers, including polyvinyl chloride (PVC), may be improved by adding a copolymer of epichlorohydrin and ethylene oxide. This reference, however, makes no mention of the fact that the antistatic properties may be further enhanced by the use of a synergistic amount of the alkylene methacrylates of the present invention.
In the Gaggar et al U.S. Patent, it was pointed out that certain properties such as tensile strength, heat distortion temperature and modulus are adversely affected by the introduction of the epichlorohydrin/ethylene oxide copolymer. Even the lower levels of loading described in the Federl et al II patent result in poorer physical properties. The use of an alkyl methacrylate polymer, such as poly (methyl methacrylate) promotes the compatibility between the base polymer and the copolymer.